Thomas Hardy's "The Darkling Thrush" was originally called "The Century's End, 1900" and was first printed in The Graphic on 29 December of that year. The hymn-like metre combines with the Romantic, Keatsian image of the thrush to produce one of Hardy's most lyrical poems

Let the poet-thrush's "happy good night air" sing us out of 2009, with all my thanks and good wishes to friends old and new, on (and behind the scenes of), Poem of the Week.

The Darkling Thrush
I leant upon a coppice gate
When Frost was spectre-grey,
And Winter's dregs made desolate
The weakening eye of day.
The tangled bine-stems scored the sky
Like strings of broken lyres,
And all mankind that haunted nigh
Had sought their household fires.
The land's sharp features seemed to be
The Century's corpse outleant,
His crypt the cloudy canopy,
The wind his death-lament.
The ancient pulse of germ and birth
Was shrunken hard and dry,
And every spirit upon earth
Seemed fervourless as I.
At once a voice arose among
The bleak twigs overhead
In a full-hearted evensong
Of joy illimited;
An aged thrush, frail, gaunt and small,
In blast-beruffled plume,
Had chosen thus to fling his soul
Upon the growing gloom.
So little cause for carolings
Of such ecstatic sound
Was written on terrestrial things
Afar or nigh around,
That I could think there trembled through
His happy good-night air
Some blessed Hope, whereof he knew
And I was unaware

"A deleted 1899 on the manuscript suggested [Hardy] had written [The Darkling Thrush] a year before," Claire Tomalin tells us in her biography, Thomas Hardy: The Time-Torn Man. Earlier in the same book, Tomalin memorably describes Hardy as a child, waiting each evening for the setting sun to light up the red-painted staircase in the family house, at which point he would recite an "evening hymn" by Sir Isaac Watts, beginning "And now another day is gone,/ I'll sing my maker's praise". "The Darkling Thrush" seems oddly to recall that scene.

It is one of Hardy's most lyrical poems, musical in execution, metaphor, theme, and even title. The Keatsian word "darkling" simply means "in the dark", but it has the sound of a preludial shimmer of birdsong. Visually, too, it prepares us for the image of the "aged thrush, frail, gaunt and small,/ In blast-beruffled plume … " Another use of the -ling suffix is to produce a diminutive of a noun (as in gosling, duckling, sapling, etc.) and though this isn't what is happening etymologically, in "darkling" we pick up a distant sense of it, and therefore of the bird's littleness and exposedness in his bare tree.
The plain, steady rhythm and rhyme-scheme of Hardy's hymn-like metre provide a kind of aural blank canvas, allowing individual words to sound out with particular clarity. Sibilance in the first three lines creates a whispery atmosphere, a touch of wind among the stiffened branches which then fall still with the alliteration-free neutrality of "The weakening eye of day". Then there are the hard 'C' sounds in stanza two: "corpse", "crypt", "cloudy canopy" – which evoke, perhaps, the tread of a funeral march, the dislodged clods of earth, the entombment of the personified century.
In the grey scenery of the first two stanzas, the narrator, barely visible, sees only the stasis of deepest winter. That resonating pair of words "leant" and "outleant" impresses on the eye images of disablement, the laying-out of the dead, and, of course, leanness.

As in the title, there is a Keatsian echo, this time from "The Eve of St Agnes". Hardy's scene is even more deathly still: it is not only the winter of the year but of a whole century. And then the solo-singer appears, and subtly the music of the diction changes. The beautifully unexpected word, "illimited", is the first we hear, inside the poem, of the singing thrush, the flowing double 'l' conveying the sense and sound of a joy which spills out and cannot be circumscribed or halted. There are further "liquid siftings" in the many l' and 'r' sounds that ensue. It's as if the broken lyre-strings that the tangled stems suggested in stanza one had been mended.

Hardy's thrush of course belongs to the Romantic tradition, in which birds seem to express emotion in "songs" that have human significance. Modern readers interpret bird-song differently: we know the "ecstatic carolings" to be territorially possessive; as mundane as estate agents' 'Sold' signs. Today's ornithologically-minded poets content themselves with more descriptive responses, though birds have never yet gone out of poetic fashion.

It would no doubt have satisfied the deep pessimist in Hardy to have known this, and one can imagine the negating final stanza he might have added to cancel the magic with gloomy thoughts of territorialism and warfare. But he is still close enough to the 19th century to be able to treat the bird, however warily, as a symbol of hope for the new epoch. And, indeed, to give the word a capital letter, which it shares only with Frost, Winter and Century itself. Later on, Hardy became more, not less, despairing: his philosophy of the "Immanent Will" is laid out in The Dynasts (which I haven't yet read, and really should get round to – New Year Resolutions, how are ye?). The heartlessness of this "Will" is more accessibly expressed in the great poem of 1912 about the sinking of the Titanic, "The Convergence of the Twain."

In 1899, however. Hardy was more optimistic. Commentators who consider the thrush to represent the poet himself surely have a good point. He was frail and bird-like in appearance, and he had discovered an abundant poetic inspiration towards the end of his life that must have seemed at times miraculously "illimited".